Group A · Loft and roof insulation
Room-in-roof insulation
Insulating the sloping ceilings, stud walls, flat ceiling, gables and dormer cheeks of an attic room.
Price by property type
Room-in-roof
- Mid-terrace£3,500–£7,000
- Semi / end-terrace£4,000–£9,000
- Detached£5,500–£12,000
- Bungalow£4,500–£9,000chalet
- Flat / block£3,000–£6,000
Before grants · updated 11 October 2026 · a survey confirms the final figure.
- Best for
- Loft conversions, dormers, attic rooms, chalet bungalows
- Guarantee or standard
- Part L; PAS 2035 if funded
- Time on site
- Typically several days to a couple of weeks, depending on how much ceiling and wall needs opening up.
- Typical price
- From £3,000
What it is
What is room-in-roof insulation?
Insulating the sloping ceilings, stud walls, flat ceiling, gables and dormer cheeks of an attic room.
Best for: Loft conversions, dormers, attic rooms, chalet bungalows.
Build-up
Room-in-roof slope
Outside
Attic room
- 1Roof covering and membrane
- 2Ventilated gap
- 3PIR boards between the rafters
- 4Insulated plasterboard
Who it suits
Which homes is room-in-roof insulation suitable for?
Is my home suitable?
Pick your property type for a straight answer on room-in-roof insulation.
Guidance only — every home is different, and a survey confirms what suits yours.
Houses
- Detached house
- Semi-detached house
- End-of-terrace
- Mid-terrace
- Townhouse
- Mews house and cottage
- Detached bungalow
- Semi and terraced bungalow
- Chalet and dormer bungalow
- Period home
- 1930s home
- Post-war and ex-council house
- Non-traditional / system-built
- Listed building or conservation area
- Farmhouse, barn conversion or rural home
- New build or self-build
Flats and blocks of flats
Commercial and public buildings
Usually suitable Depends — a survey confirms
Not usually suitable for 1 property type
- Park and mobile home — Park and mobile homes need specialist systems, which we arrange through a partner rather than standard measures.
Materials and brands
What we use
Sloping ceilings, stud (knee) walls, flat ceiling, gable walls and dormer cheeks; PIR boards plus insulated plasterboard.
Insulation brands we work with
- Knauf Insulation (Earthwool, Supafil blown)
- Rockwool
- Superglass
- Isover
- Kingspan
- Celotex
- Recticel
- Xtratherm
- Steico wood-fibre
- YBS and Actis multifoil
The exact system and brand for your home are confirmed in your written quote.
Heat, bills and EPC
What it does for your heat loss, bills and EPC
Heat rises, so a poorly insulated roof is often the largest single route out for heat. Insulating it lowers the roof's U-value — how easily heat passes through — so the heating runs less and the EPC rating usually improves. The gain is largest where there's little insulation now; topping up a loft that's already reasonably insulated gains less.
See the EPC points and savings for your home in the EPC plannerU-value before and after, typical heat and bill saving, and EPC points — worked out for your property.Price
How much does room-in-roof insulation cost?
Prices change with your property type. Pick your column — the quote builder then refines it for your home.
| Measure | Mid-terrace | Semi / end-terrace | Detached | Bungalow | Flat / block |
|---|---|---|---|---|---|
| Room-in-roof | £3,500–£7,000 | £4,000–£9,000 | £5,500–£12,000 | £4,500–£9,000chalet | £3,000–£6,000 |
Indicative ranges for London and the South East, supplied and installed, including VAT, before grants. Updated 11 October 2026. A survey confirms your final price.
0% VAT on energy-saving materials
Insulation, solar panels, batteries and heat pumps installed in homes in Great Britain are zero-rated for VAT until 31 March 2027. Windows and doors are not included.What to expect
Time on site, disruption and approvals
Time on site
Typically several days to a couple of weeks, depending on how much ceiling and wall needs opening up.
Disruption
Moderate — the attic room is out of use while we work, with plastering at the end. The rest of the house carries on as normal.
Planning and building control
Insulating an existing room-in-roof is done to Building Regulations Part L. If it's funded, the work follows PAS 2035, with a retrofit assessment first.
Guarantee and standard
Part L; PAS 2035 if funded. The guarantee and certification for your job are confirmed in writing in your quote.
60-second grant check
Could a grant help pay for it?
Grant eligibility checker
About 60 seconds · plain results: likely, possibly or not eligible
Before we start
What type of property is it?
Questions
Room-in-roof insulation: your questions answered
How much does room-in-roof insulation cost?
Typical installed prices in London and the South East, including VAT and before any grant: £3,500–£7,000 for a mid-terrace; £4,000–£9,000 for a semi-detached or end-of-terrace house; £5,500–£12,000 for a detached house; £4,500–£9,000 for a bungalow (chalet); £3,000–£6,000 for a flat. Prices updated 11 October 2026. A survey confirms your final figure.
What is room-in-roof insulation?
Insulating every part of an attic room that touches the cold: the sloping ceilings, the short stud (knee) walls, the flat ceiling at the top, gable walls and dormer cheeks. Missing any one of them leaves a cold spot.
Can I get funding for room-in-roof insulation?
You may. Room-in-roof is one of the insulation measures ECO4 can fund for eligible households, depending on eligibility. Funded jobs follow PAS 2035, so a retrofit assessment comes first.
Will I lose headroom?
A little, because insulation and new plasterboard go on the inside of the slopes. We use slim PIR boards and insulated plasterboard to keep the loss as small as possible.
Do I need to move out?
No. The attic room is out of use while we work, but the rest of the house carries on as normal.
Group A
More in loft and roof insulation
Loft insulation
Mineral wool laid between and across the joists to 270–300 mm so heat stays in the rooms below.
Loft insulation top-up
An extra cross-layer over existing insulation to reach the recommended 270 mm or more.
Blown loft insulation
Loose-fill insulation blown into awkward, shallow or low-headroom lofts that rolls can't reach.
Loft clearance and replacement
Old, damp or damaged insulation removed, the loft cleaned, then new mineral wool fitted.
Raised loft boarding and storage
Loft legs or raised boarding over full-depth insulation, so storage doesn't crush it.
Insulated loft hatch and ladders
An insulated, draught-sealed hatch and loft ladder — a small add-on that stops a big leak.
Begin your project
Price room-in-roof insulation in two minutes
See a price range for your property type, with grants and 0% VAT applied where they fit. A survey always confirms the final figure.